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Making Sense of Carbonate Previous HitPoreNext Hit Previous HitSystemsNext Hit: Implication for Porosity Cut-Off and STOOIP

Arve Lønøy
Norsk Hydro ASA, P.O. Box 7190, N-5020 Bergen, Norway

 

The most widely used Previous HitporeNext Hit type Previous HitsystemsNext Hit are limited by the fact that the relation between porosity and permeability is poorly defined. Furthermore, these Previous HitsystemsNext Hit do not optimally integrate sedimentology, diagenesis and flow-related properties. In many carbonate reservoirs it is therefore difficult to generate predictive models for reservoir quality distribution, giving significant uncertainty in STOOIP calculations.

Based on empirical data, mostly from Europe and the Middle East, a new system for carbonate Previous HitporeNext Hit types has been developed. The new system uses elements from the Choquette & Pray (1970) and Lucia (1983) Previous HitporeNext Hit type classification Previous HitsystemsNext Hit, but also introduces many new elements. The new Previous HitporeNext Hit type system includes 14 Previous HitporeNext Hit type classes, which show a predictable relationship between porosity and permeability. It combines sedimentological/diagenetic features and flow-related properties, and reservoir critical parameters can thus to some extent be predicted using sedimentological and diagenetic models.

The new classification system significantly improves porosity to permeability relationship for individual Previous HitporeNext Hit types, with coefficient of determination (R2) mostly in the range of 0.7-0.9. Porosity cut-offs derived from the cross-plots show significant variability among the different Previous HitporeNext Hit types, ranging from 5% to 30% porosity cut-off at 1 mD permeability. This has a major impact on STOOIP calculation as it strongly affects net/gross. Simple models run on four different oil reservoirs and prospects indicate that STOOIP calculations may vary with up to several hundred percent based on which Previous HitporeNext Hit type or Previous HitporeTop type combinations that have been used in the model.